Electric discharge device



July 21, 1931. E. E. CHARLTON ELECTRIC DISCHARGE DEVICE Filed July 17,1924 Patented July 21, 1931 -UNITED STATES PATENT OFFICE ERNEST E.CHARLTON, OF SCHENECTADY, NEW YORK, ASSIGNOR T GENERAL ELEC- A TRIOCOMPANY, A CORPORATION 0F NEW 'YORK ELECTRIC DISCHARGE DEVICEApplication mea July 17,

the efliciency and current-carrying capacity`v of this type ofrectifier.

1o My invention relates particularly to the class of gas ionizationrectifiers in'which a cathode is employed having a relatively muchlarger surface than the anode, thereby obtaining an asymmetricconductivity. Heretofore, these rectifiers have been made only for halfwave rectification.

The provision of more than one anode in such a rectifier is notsufiicient alone to secure efficient full wa-.ve rectification, as arelatively large current flows between the anodes in the gas which notonly wastes energy and reduces the efficiency of the device but thedischarge between the anodes will eventually change to an arc discharge.The tendencyfor discharges between the anodes to occur will make therectification unstable. In accordance with my invention, I have provideda rectifier having a plurality of anodes in which the cathode is sodisposed between the anodes as to largely suppress the I undesired flowof current between the anodes, and to produce stable rectification. Ihave provided several forms of rectifiers in all of which the cathodeacts as a shield between the anodes, but which differ somewhat in theirconstruction. For example in one form of my invention the shielding ismore complete than in the simplest form to permit operation at highervoltages and in still another form an apertured envelope oflnon-conducting material is provided about the one or both anodes topermit rectification of current of still higher voltage.

The novel features of my invention will be described with greater detailin the following specification taken in connection with the accompanyingdrawings in which Fig. 1 illustrates in perspectivea simple form ofrectifier forA the rectification of currents ofl moderate voltage; Fig.2 is a perspective 1924. Serial No. 728,638.

view which is partly in vertical section of another formo highercurrent-carrying capacity; Fig. 3 illustrates a third form of myinvention, of still higher current-carrying capacity, this view alsobeing partly in vertical section; Fig. 4 is a diagram of electricalconnections which may be used for my improved device; and Fig. 5 is afragmental View of a modication..

The device'shown in Fig. 1 comprises a bulb 1 in which are mounted aplate-shaped cathode 2 and anodes 3, 4 which are located on oppositesides of and closely adjacent to the cathode 2. The cathode 2 which isof the unheated or self-sustaining discharge type may vrconsist ofnickel, iron, molybdenum, tantalum, or of other metals which can bereadily shaped into plate form and which are not easily vaporized atmoderately high temperatures. The anodes 3, 4 in the device shown inthis figure consist of wires of tungsten, nickel or of other suitablemetal. Tungsten is preferred as it may be readily sealed through theprojections 5, 6 of the. hard glass stem 7, only short sections of thewires projecting beyond the glass. The anode wires are led through theglass stem and are connected to the contacts 8, 9 of theIl bayonet typebase 10. The cathode conductor 11 is sealed to a contact 12 of the base.

The bulb 1 is charged with a suitable gas which at the operatingtemperature of the device will have a density high enough to produce adesired conductivity by ionization. For example, the bulb may be chargedwith helium and neon as the ionization medium. Helium is much to bepreferred. The pressure of the gaseous filling may be varied betweenwide limits depending upon the characteristic of the gas, the operatinvoltage. the geometric construction of the evice, the current-carryingcapacity and other tube conditions. In general the pressure of the gasmay be varied between the limits of about terial which is chemicallyreactive toward gaseous impurities, or is otherwise capable of removingcontaminating gas, such as water vapor, oxygen, hydrogen and nitrogen.For example, I may apply to one of the electrodes a small quantity ofmetallic magnesium, calcium or the like and then after the bulb has beenexhausted, freed from water vapor, and charged'with helium or otherdesired gas, the electrodes are heated by a. high frequency field to thevapolizing temperature of tlie magnesium, or other alkali earth metal,thereby depositing,r a film of this metal on the walls of the bulb. Thevoltage consumption in the device is lowered about 20% by the presenceof a film of finely divided magnesium.

The voltage drop may be st1ll further lowered with an accompanymglncrease of etliciencj; by admitting an alkali metal, preferably csiumor rubidium into the bulb before the magnesium is vaporized andoxidizing the alkali metal as by admitting a little oxygen and warmingthe bulb. The oxidevof the alkali metal appears toreadily combine withhydrogen which is liberated during the operation of the rectifier,probably by the decomposition of water vapor given off by the bulb. Bythe use of caesium oxide together with magnesium I have reduced thevoltage drop to less than one-half its original value. This chemicaladdition to the gas atmosphere whereby the voltage drop is lowered iscovered by my application, Ser. No. 726,640.

As shown in Fig. 4, the rectifier maybe used by connecting the anodes 3,4 to the opposite terminals of a source of alternating current, such asthe terminals of the secondary of a transformer 13, while the cathode isconnected by a conductor 14 in series with a load 15 to an intermediatepoint on the transformer secondary.

The load 15 here has been represented as a non-inductive resistance,having voltage taps whereby rectified current at different voltages maybe made available forA radio systems or other purposes. The rectifier,of

course. may be used to furnish rectified current for other loads, suchas storage batteries, or direct current instruments. A steady currentcondition may be produced by the use of a wave filter consisting of aseries reactance 27, and shunt condensers 28, 29.

In the device shown in Fig. 2, the cathode surface is even larger withrespect to the anode surface than in the device shown in Fig. 1. Thecathode assumes the form of two substantially cylindrical housings 16,17 surrounding the respective anodes 3, 4.-.

These housings, which are electricallv connected together, as indicatedat 31, are mounted on the stem 7 which is sealed in the 4bulb l.l Inthis form of my invention the area of the cathode is about 300 timesgreater much larger rod-like bodies which are mounted upon theleading-in conductors 20, 21. In order to reduce theeff'ective area ofthese anodes 18, 19 and thereby to give a rectifying characteristic tothe device,l these anodes are respectively surrounded by insulatingenvelopes or shrouds 22, 23, which are spaced closely adjacent to theanodes at the sides but are spaced away from the end face of the anodes.Apertures 24, 25 of restricted size are provided in these envelopes atthe ends, which are spaced away from the anodes. In some cases, as'shownin Fig'. 5,la conductive coating 26 maybe rovided to advantage upon theinner surl ace of tlie anode shrouds. The anodes in this case areconnected to the conductive coating upon the inside of the shroud. InFig. 5, the anode 19 is connected to the coating26 by a suitableconductor 30, in this case a'.` helical spring sprung between the anodeand the surrounding envelope. When this device is charged. with asuitable gas, such as helium, a glow discharge can readily pass from theelectrodes 18,- 19 alternately to the surrounding cathode constituted bythe members 16, 17.

As the polarity of the electrodes 18, 19 alternates current fiows to thecathode alternately from the anodes 18, 19 during the intervals wheneach respective anode is positive. In other words, the apertures 24, 25in the envelopes 22,23 surrounding the respective anodes do not preventthe passage of electrons from the outer casing constituting the cathodeto the anodes but due to their relatively small diameter they willprevent electron flow in the opposite direction. Apparently a negativecharge accumulatesupon the inner surface of the anode shrouds 22, 23which repels the electrons emanating from the electrodes 18, 19, largelysuppressing current flow between the electrodes 18, 19. Arelativelylarge currentA can flow in the opposite direction as little or no`negative charge can accumulate on the outside ofthe envelopes 22, 23.Such a charge will be neutralized by the more active positiveionizmation occurring in the space' between the shrouds and the cathodes,16, 17.

Furthermore, a negative charge on the outside, evenv if present, wouldnot be so effective in suppressingv current flow as a charge on theinside. Whatever may be the mechanism of'conduction, I have obtainedsub- ,vez

stantially complete rectilication with devices 4therein, sleeves ofinsulating material closely as shown in Fig.' 3 with impressed mean ef-dfective voltages between the electrodes 18, 19 higher than 2,000 volts.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

l. An electric discharge device comprising a container terminating in areentrant stem, a plurality of anodes therein, a cathode of theself-sustaining discharge type having a materially largersurface thansaid anodes, said cathode constituting a shield between said anodes andbeing closely adjacent thereto, all of said electrodes being surportedsolely from said stem and an ioniza le gas in said container having atthe operating temperature of said device a pressure sufiiciently highto. conduct an ionization current be'- tween said electrodes.y

2. An -electric discharge device comprising a plurality of point anodes,a cathode of the self-sustaining discharge type which has a materiallylarger surface than said respec- :ill

tive anodes, said cathode being closely adjacent to and substantiallysurroundingI the anodes and having a portion intermediate said anodes tothereby shield them from one another, an enclosing container and anattenuated'gas in said container.

3. A rectifier comprising a plurality of anodes, a cathode constitutedby a conductive practically complete housin surrounding each ofsaidrespective anodges and acting to shield said anodes from oneanother, said anodes each having a materially smaller surface thansaid-cathode, an enclosing container and a gaseous filling of inert gastherein ata pressure of about 5 to 80 millimeters of mercury.

4. An' electrical discharge device comprising a plurality of anodes, acathode located Ybetween and constituting a shield for said anodes andshrouds ofl non-conductive material, each havin an aperture,'respectively surrounding sai anodes, van enclosing con tainer and afilling of gas in said container mert with respect to said electrodesand having a pressure at operating temperatures which is suiiicientlyhigh to produce a substantial current-carrying capacity by beingionized.

5. A rectifier comprising 'a plurality of i anodes consisting ofdiicultly vaporizable metal, insulating envelopes therefor closelysurrounding the sides of said anodes, and

.each having an aperture opposite the endsA of surrounding all but anexposed tip of said anodes,elongatedhousings of sheet metal revspectively enclosing said anodes and being electrically connected toconstitute a common cathode and a chargeof attenuated gas in saidcontainer e 7. A rectifier for alternating current com- -prising acontainer, a stem projecting into said container, said stem having aplurality of elongated extensions, wires sealed respectively into saidstems and each having a tip protruding from said respective extensions,4 metal housings mounted upon said stem and respectively surrounding thetips of said wires, an electric connection between said' housings,external contacts for said wires and said housings and a charge of gasin said container at a pressure of the order of 5 to 80 millimeters ofmercury. f

8. A rectifier for alternating current comprising a container, aplurality of anodes located therein, 'a cathode constituting aconductive housing substantially surrounding each of said respectiveanodes and constituting a barrier between said anodes, said cathodehaving a materially largersurface than either of said anodes,aperturedshrouds'consisting of insulating material ,respectively locatedbetween said anodes and said cathode and a readilys ionizable gaseousmedium 'in said container.

In witness whereof, I have hereunto set my hand this 16th day if July,1924.

ERNEST E. CHARLTON.

said anodes'and spaced away therefrom, a f I y cathode having aplurality ofmembers respectlvely surrounding said envelopes and spacedaway therefrom," a'. surroundm container and a charge of rare gas inLsai container at a pressure of about 19 millimeters of mercury.

040A rectifier for alternatin current compricing a container, a plura tyof anodes

